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X9421
Single Digitally Controlled (XDCP) Potentiometer
FEATURES
Single Voltage Potentiometer
64 Resistor Taps
SPI Serial Interface for write, read, and transfer
operations of the potentiometer
Wiper Resistance, 150
Typical at 5V
4 Non-Volatile Data Registers
Non-Volatile Storage of Multiple Wiper Positions
Power On Recall. Loads Saved Wiper Position on
Power Up.
Standby Current < 5A Max
V
CC
: 2.7V to 5.5V Operation
2.5K
, 10K
End to End Resistance
100 yr. Data Retention
Endurance: 100, 000 Data Changes per Bit per
Register
14-Lead TSSOP, 16-Lead SOIC
Low Power CMOS
DESCRIPTION
The X9421 integrates a single digitally controlled
potentiometer (XDCP) on a monolithic CMOS
integrated circuit.
The digital controlled potentiometer is implemented
using 63 resistive elements in a series array. Between
each element are tap points connected to the wiper
terminal through switches. The position of the wiper on
the array is controlled by the user through the SPI bus
interface. The potentiometer has associated with it a
volatile Wiper Counter Register (WCR) and a four non-
volatile Data Registers that can be directly written to
and read by the user. The contents of the WCR
controls the position of the wiper on the resistor array
though the switches. Powerup recalls the contents of
the default data register (DR0) to the WCR.
The XDCP can be used as a three-terminal
potentiometer or as a two terminal variable resistor in
a wide variety of applications including control,
parameter adjustments, and signal processing.
BLOCK DIAGRAM
64-taps
10K
inc / dec
R
H
/V
H
R
L
/V
L
R
W
/V
W
POT
V
CC
V
SS
SPI
bus
address
data
status
write
read
wiper
transfer
Power On Recall
Wiper Counter
Register (WCR)
Data Registers
4 Bytes
control
interface
Bus
Interface &
Control
Low Noise/Low Power/SPI Bus
A
PPLICATION
N
OTES
A V A I L A B L E
AN99 AN115 AN120 AN124 AN133 AN134 AN135
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CIRCUIT LEVEL APPLICATIONS
Vary the gain of a voltage amplifier
Provide programmable dc reference voltages for
comparators and detectors
Control the volume in audio circuits
Trim out the offset voltage error in a voltage amplifier
circuit
Set the output voltage of a voltage regulator
Trim the resistance in Wheatstone bridge circuits
Control the gain, characteristic frequency and
Q-factor in filter circuits
Set the scale factor and zero point in sensor signal
conditioning circuits
Vary the frequency and duty cycle of timer ICs
Vary the dc biasing of a pin diode attenuator in RF
circuits
Provide a control variable (I, V, or R) in feedback
circuits
SYSTEM LEVEL APPLICATIONS
Adjust the contrast in LCD displays
Control the power level of LED transmitters in
communication systems
Set and regulate the DC biasing point in an RF
power amplifier in wireless systems
Control the gain in audio and home entertainment
systems
Provide the variable DC bias for tuners in RF
wireless systems
Set the operating points in temperature control
systems
Control the operating point for sensors in industrial
systems
Trim offset and gain errors in artificial intelligent
systems
DETAILED FUNCTIONAL DIAGRAM
WIPER
COUNTER
REGISTER
(WCR)
R
H
/V
H
R
L
/V
L
DATA
R
W
/V
W
INTERF
A
CE
AND
CONTROL
CIRCUITR
Y
V
CC
V
SS
CS
SCK
A0
SO
SI
HOLD
WP
Control
64--taps
10K
Power On Recall
DR0
DR1
DR2 DR3
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PIN CONFIGURATION
V
CC
R
L
/V
L
VSS
1
2
3
4
5
6
7
8
14
13
12
11
10
9
NC
R
W
/V
W
SCK
CS
TSSOP
R
H
/V
H
X9421
S0
NC
SI
HOLD
WP
A0
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
SOIC
X9421
V
CC
R
L
/V
L
R
W
/V
W
R
H
/V
H
HOLD
WP
A0
NC
VSS
SCK
CS
NC
SI
SO
NC
NC
PIN ASSIGNMENTS
TSSOP pin
SOIC pin
Symbol
Brief Description
1
2
SO
Serial Data Output
2
3
NC
No Connect
3
NC
No Connect
4
4
CS
Chip Select
5
5
SCK
Serial Clock
6
6
SI
Serial Data Input
7
8
V
SS
System Ground
8
9
WP
Hardware Write Protect
9
10
A0
Device Address
10
11
HOLD
Device select. Pause the serial bus.
11
12
R
W
/ V
W
Wiper Terminal of the Potentiometer.
12
13
R
H
/ V
H
High Terminal of the Potentiometer.
13
14
R
L
/ V
L
Low Terminal of the Potentiometer.
14
16
V
CC
System Supply Voltage
1
NC
No Connect
7
NC
No Connect
15
NC
No Connect
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PIN DESCRIPTIONS
Host Interface Pins
Serial Output (SO)
SO is a push/pull serial data output pin. During a read
cycle, data is shifted out on this pin. Data is clocked out
by the falling edge of the serial clock.
Serial Input
SI is the serial data input pin. All opcodes, byte
addresses and data to be written to the potentiometer
and pot register are input on this pin. Data is latched by
the rising edge of the serial clock.
Serial Clock (SCK)
The SCK input is used to clock data into and out of the
X9421.
Chip Select (CS)
When CS is HIGH, the X9421 is deselected and the
SO pin is at high impedance, and (unless an internal
write cycle is underway) the device will be in the
standby state. CS LOW enables the X9421, placing it
in the active power mode. It should be noted that after
a power-up, a HIGH to LOW transition on CS is
required prior to the start of any operation.
Hold (HOLD)
HOLD is used in conjunction with the CS pin to select
the device. Once the part is selected and a serial
sequence is underway, HOLD may be used to pause
the serial communication with the controller without
resetting the serial sequence. To pause, HOLD must
be brought LOW while SCK is LOW. To resume
communication, HOLD is brought HIGH, again while
SCK is LOW. If the pause feature is not used, HOLD
should be held HIGH at all times.
Device Address (A
0
)
The address input is used to set the least significant bit
of the 8-bit slave address. A match in the slave address
serial data stream must be made with the address
input in order to initiate communication with the X9421.
A maximum of 2 devices may occupy the SPI serial
bus.
Potentiometer Pins
V
H
/R
H
, V
L
/R
L
The V
H
/R
H
and V
L
/R
L
inputs are equivalent to the
terminal connections on either end of a mechanical
potentiometer.
V
W
/R
W
The wiper output is equivalent to the wiper output of a
mechanical potentiometer.
Hardware Write Protect Input (WP)
The WP pin when LOW prevents nonvolatile writes to
the Data Registers. Writing to the Wiper Counter
Register is not restricted.
System/Digital Supply (V
CC
)
V
CC
is the supply voltage for the system/digital section.
V
SS
is the system ground.
PRINCIPLES OF OPERATION
The X9421 is a highly integrated microcircuit
incorporating a resistor array and associated registers
and counter and the serial interface logic providing
direct communication between the host and the XDCP
potentiometer.
Serial Interface
The X9421 supports the SPI interface hardware
conventions. The device is accessed via the SI input
with data clocked in on the rising SCK. CS must be
LOW and the HOLD and WP pins must be HIGH
during the entire operation.
The SO and SI pins can be connected together, since
they have three state outputs. This can help to reduce
system pin count.
Array Description
The X9421 is comprised of one resistor array
containing 63 discrete resistive segments that are
connected in series. The physical ends of each array
are equivalent to the fixed terminals of a mechanical
potentiometer (V
H
/R
H
and V
L
/R
L
inputs).
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At both ends of the array and between each resistor
segment is a CMOS switch connected to the wiper
(V
W
/R
W
) output. Within the individual array only one
switch may be turned on at a time.
These switches are controlled by a Wiper Counter
Register (WCR). The six bits of the WCR are decoded
to select, and enable, one of sixty-four switches. The
block diagram of the potentiometer is shown in Figure 1.
Wiper Counter Register (WCR)
The X9421 contains a Wiper Counter Register. The
WCR can be envisioned as a 6-bit parallel and serial
load counter with its outputs decoded to select one of
sixty-four switches along its resistor array. The
contents of the WCR can be altered in four ways: it
may be written directly by the host via the Write Wiper
Counter Register instruction (serial load); it may be
written indirectly by transferring the contents of one of
four associated Data Registers via the XFR Data
Register instruction (parallel load); it can be modified
one step at a time by the Increment/ Decrement
instruction. Finally, it is loaded with the contents of its
data register zero (DR0) upon power-up.
The Wiper Counter Register is a volatile register; that
is, its contents are lost when the X9421 is powered-
down. Although the register is automatically loaded
with the value in DR0 upon power-up, this may be
different from the value present at power-down.
Data Registers
The potentiometer has four 6-bit nonvolatile Data
Registers. These can be read or written directly by the
host. Data can also be transferred between any of the
four Data Registers and the WCR. It should be noted all
operations changing data in one of the Data Registers is
a nonvolatile operation and will take a maximum of 10ms.
If the application does not require storage of multiple
settings for the potentiometer, the Data Registers can
be used as regular memory locations for system
parameters or user preference data.
Register Descriptions
Table 1. Data Registers, (6-bit), Nonvolatile
There are four 6-bit Data Registers associated with the
potentiometer.
{D5~D0}: These bits are for general purpose Nonvol-
atile data storage or for storage of up to four different
wiper values.
Table 2. Wiper Counter Register, (6-bit), Volatile
{WP5~WP0}: These bits specify the wiper position of
the potentiometer.
0
0
D5
D4
D3
D2
D1
D0
(MSB)
(LSB)
0
0
WP5 WP4 WP3 WP2 WP1 WP0
(MSB)
(LSB)
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Write in Process
The contents of the Data Registers are saved to
nonvolatile memory when the CS pin goes from LOW
to HIGH after a complete write sequence is received by
the device. The progress of this internal write operation
can be monitored by a Write In Process bit (WIP). The
WIP bit is read with a Read Status command.
INSTRUCTIONS
Address/Identification (ID) Byte
The first byte sent to the X9421 from the host, following
a CS going HIGH to LOW, is called the Address or
Identification byte. The most significant four bits of the
slave address are a device type identifier, for the
X9421 this is fixed as 0101[B] (refer to Figure 2).
The least significant bit in the ID byte selects one of
two devices on the bus. The physical device address is
defined by the state of the A
0
input pin. The X9421
compares the serial data stream with the address input
state; a successful compare of the address bit is
required for the X9421 to successfully continue the
command sequence. The A
0
input can be actively
driven by a CMOS input signal or tied to V
CC
or V
SS
.
The remaining three bits in the ID byte must be set to
110.
Figure 2. Address/Identification Byte Format
Instruction Byte
The next byte sent to the X9421 contains the
instruction and register pointer information. The four
most significant bits are the instruction. The next two
bits point to one of four Data Registers. The format is
shown below in Figure 3.
Figure 3. Instruction Byte Format
1
0
0
1
1
0
A0
Device Type
Identifier
Device Address
1
I1
I2
I3
I0
R1
R0
0
0
Register
Select
Instructions
Figure 1. Detailed Potentiometer Block Diagram
Serial Data Path
From Interface
Circuitry
Register 0
Register 1
REGISTER 2
REGISTER 3
Serial
Bus
Input
Parallel
Bus
Input
Counter
Register
INC/DEC
Logic
UP/DN
CLK
Modified SCK
UP/DN
V
H
V
L
V
W
8
6
C
O
U
N
T
E
R
D
E
C
O
D
E
IF WCR = 00[H] THEN V
W
= V
L
IF WCR = 3F[H] THEN V
W
= V
H
Wiper
(WCR)
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The four high order bits of the instruction byte specify
the operation. The next two bits (R
1
and R
0
) select one
of the four registers that is to be acted upon when a
register oriented instruction is issued. The last two bits
are defined as 0.
Two of the eight instructions are two bytes in length and
end with the transmission of the instruction byte. These
instructions are:
XFR Data Register to Wiper Counter Register --This
instruction transfers the contents of one specified
Data Register to the Wiper Counter Register.
XFR Wiper Counter Register to Data Register--This
instruction transfers the contents of the Wiper
Counter Register to the specified associated Data
Register.
The basic sequence of the two byte instructions is
illustrated in Figure 4. These two-byte instructions
exchange data between the WCR and one of the Data
Registers. A transfer from a Data Register to a WCR is
essentially a write to a static RAM, with the static RAM
controlling the wiper position. The response of the
wiper to this action will be delayed by t
WRL
. A transfer
from the WCR (current wiper position), to a Data
Register is a write to nonvolatile memory and takes a
minimum of t
WR
to complete. The transfer can occur
between the potentiometer and one of its associated
registers.
Five instructions require a three-byte sequence to
complete. These instructions transfer data between the
host and the X9421; either between the host and one
of the Data Registers or directly between the host and
the WCR. These instructions are:
Read Wiper Counter Register--read the current
wiper position of the pot,
Write Wiper Counter Register--change current wiper
position of the pot,
Read Data Register--read the contents of the
selected data register;
Write Data Register--write a new value to the
selected data register.
Read Status--This command returns the contents of
the WIP bit which indicates if the internal write cycle
is in progress.
The sequence of these operations is shown in Figure 5
and Figure 6.
The final command is Increment/Decrement. It is
different from the other commands, because it's length
is indeterminate. Once the command is issued, the
master can clock the wiper up and/or down in one
resistor segment steps; thereby, providing a fine tuning
capability to the host. For each SCK clock pulse (t
HIGH
)
while SI is HIGH, the selected wiper will move one
resistor segment towards the V
H
/R
H
terminal. Similarly,
for each SCK clock pulse while SI is LOW, the selected
wiper will move one resistor segment towards the
V
L
/R
L
terminal. A detailed illustration of the sequence
and timing for this operation are shown in Figure 7 and
Figure 8.
Figure 4. Two-Byte Instruction Sequence
0
1
0
1
1
1
0
A0
I3
I2
I1
I0
R1
R0
0
0
SCK
SI
CS
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Figure 5. Three-Byte Instruction Sequence (Write)
Figure 6. Three-Byte Instruction Sequence (Read)
Figure 7. Increment/Decrement Instruction Sequence
Figure 8. Increment/Decrement Timing Limits
0
1
0
1
0
A0
I3
I2
I1 I0
R1 R0
0
0
SCL
SI
0
0
D5 D4 D3 D2
D1 D0
CS
1
1
0
1
0
1
0
A0
I3
I2
I1 I0
R1 R0 0
0
SCL
SI
CS
1
1
S0
0
0
D5 D4 D3 D2
D1 D0
Don't Care
0
1
0
1
1
1
0
A0
I3
I2
I1
I0
0
0
0
SCK
SI
I
N
C
1
I
N
C
2
I
N
C
n
D
E
C
1
D
E
C
n
0
CS
SCK
SI
V
W
INC/DEC CMD Issued
t
WRID
Voltage Out
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Table 3. Instruction Set
Instruction
Instruction Set
Operation
I
3
I
2
I
1
I
0
R
1
R
0
Read Wiper Counter
Register
1
0
0
1
0
0
0
0
Read the contents of the Wiper Counter Register
Write Wiper Counter
Register
1
0
1
0
0
0
0
0
Write new value to the Wiper Counter Register
Read Data Register
1
0
1
1
1/0
1/0
0
0
Read the contents of the Data Register pointed to
by R
1
R
0
Write Data Register
1
1
0
0
1/0
1/0
0
0
Write new value to the Data Register pointed to by
R
1
R
0
XFR Data Register to
Wiper Counter
Register
1
1
0
1
1/0
1/0
0
0
Transfer the contents of the Data Register pointed
to by R
1
R
0
to the Wiper Counter Register
XFR Wiper Counter
Register to Data
Register
1
1
1
0
1/0
1/0
0
0
Transfer the contents of the Wiper Counter
Register to the Data Register pointed to by R
1
R
0
Increment/Decrement
Wiper Counter
Register
0
0
1
0
0
0
0
0
Enable Increment/decrement of the Wiper Counter
Register
Read Status (WIP bit)
0
1
0
1
0
0
0
1
Read the status of the internal write cycle, by
checking the WIP bit.
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Instruction Format
Notes: (1)
"A0": stands for the device addresses sent by the master.
(2)
WPx refers to wiper position data in the Wiper Counter Register
"I": stands for the increment operation, SI held HIGH during active SCK phase (high).
(3)
"D": stands for the decrement operation, SI held LOW during active SCK phase (high).
Read Wiper Counter Register (WCR)
Write Wiper Counter Register (WCR)
Read Data Register (DR)
Read the contents of the Register pointed to by R1-R0.
Write Data Register (DR)
Write a new value to the Register pointed to by R1-R0.
Transfer Data Register (DR) to Wiper Counter Register (WCR)
Transfer the contents of the Register pointed to by R1-R0 to the WCR.
CS
Falling
Edge
device type
identifier
device
addresses
instruction
opcode
wiper position
(sent by X9421 on SO)
CS
Rising
Edge
0
1
0
1
1
1
0
A
0
1
0
0
1
0
0
0
0
0
0
W
P
5
W
P
4
W
P
3
W
P
2
W
P
1
W
P
0
CS
Falling
Edge
device type
identifier
device
addresses
instruction
opcode
Data Byte
(sent by Host on SI)
CS
Rising
Edge
0
1
0
1
1
1
0
A
0
1
0
1
0
0
0
0
0
0
0
W
P
5
W
P
4
W
P
3
W
P
2
W
P
1
W
P
0
CS
Falling
Edge
device type
identifier
device
addresses
instruction
opcode
register
addresses
Data Byte
(sent by X9421 on SO)
CS
Rising
Edge
0
1
0
1
1
1
0
A
0
1
0
1
1
R
1
R
0
0
0
0
0
W
P
5
W
P
4
W
P
3
W
P
2
W
P
1
W
P
0
CS
Falling
Edge
device type
identifier
device
addresses
instruction
opcode
register
addresses
Data Byte
(sent by host on SI)
CS
Rising
Edge
HIGH-VOLTAGE
WRITE CYCLE
0 1 0 1 1 1 0
A
0
1 1 0 0
R
1
R
0
0 0 0 0
W
P
5
W
P
4
W
P
3
W
P
2
W
P
1
W
P
0
CS
Falling
Edge
device type
identifier
device
addresses
instruction
opcode
register
addresses
CS
Rising
Edge
0 1 0 1 1 1 0
A
0
1 1 0 1
R
1
R
0
0 0
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Transfer Wiper Counter Register (WCR) to Data Register (DR)
Increment/Decrement Wiper Counter Register (WCR)
Read Status
CS
Falling
Edge
device type
identifier
device
addresses
instruction
opcode
register
addresses
CS
Rising
Edge
HIGH-VOLTAGE
WRITE CYCLE
0 1 0 1 1 1 0
A
0
1 1 1 0
R
1
R
0
0 0
CS
Falling
Edge
device type
identifier
device
addresses
instruction
opcode
increment/decrement
(sent by master on SDA)
CS
Rising
Edge
0
1
0
1
1
1
0
A
0
0
0
1
0
0
0
0
0 I/D I/D
.
.
.
.
I/D I/D
CS
Falling
Edge
device type
identifier
device
addresses
instruction
opcode
Data Byte
(sent by X9421 on SO)
CS
Rising
Edge
0
1
0
1
1
1
0
A
0
0
1
0
1
0
0
0
1
0
0
0
0
0
0
0
W
I
P
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ABSOLUTE MAXIMUM RATINGS
Temperature under bias . . . . . . . . . . . . 65
C to +135
C
Storage temperature . . . . . . . . . . . . . . 65
C to +150
C
Voltage on SCK any address input
with respect to V
SS
. . . . . . . . . . . . . . . . . 1V to +7V
V = | (V
H
V
L
) | . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5V
Lead temperature (soldering, 10 seconds) . . . . . . 300
C
I
W
(10 seconds) . . . . . . . . . . . . . . . . . . . . . . . . 6mA
Any V
H
/R
H
, V
L
/R
L
, V
W
/R
W
. . . . . . . . . . . . V
SS
to V
CC
COMMENT
Stresses above those listed under "Absolute Maximum
Ratings" may cause permanent damage to the device.
This is a stress rating only; functional operation of the
device (at these or any other conditions above those
listed in the operational sections of this specification) is
not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device
reliability.
RECOMMENDED OPERATING CONDITIONS
Temp
Min.
Max.
Commercial
0C
+70C
Industrial
40C
+85C
Device
Supply Voltage (V
CC
) Limits
X9421
5V
10%
X9421-2.7
2.7V to 5.5V
ANALOG CHARACTERISTICS (Over recommended operating conditions unless otherwise stated.)
Notes: (1)
Absolute Linearity is utilized to determine actual wiper voltage versus expected voltage as determined by wiper position when
used as a potentiometer.
(2)
Relative Linearity is utilized to determine the actual change in voltage between two successive tap positions when used as a
potentiometer. It is a measure of the error in step size.
(3)
MI = RTOT/63 or (V
H
V
L
)/63, single pot
(4)
Typical = Individual array resolution.
Symbol
Parameter
Limits
Test Conditions
Min.
Typ.
Max.
Units
End to End Resistance Tolerance
20
%
Power Rating
50
mW
25C, each pot
I
W
Wiper Current
3
mA
R
W
Wiper Resistance
150
250
Wiper Current =
1mA,
V
CC
= 5V
400
1000
Wiper Current =
1mA,
V
CC
= 3V
V
TERM
Voltage on any V
H
/R
H
, V
L
/R
L
, V
W
/R
W
V
SS
V
CC
V
V
SS
= 0V
Noise
-120
dBV
Ref: 1kHz
Resolution
(4)
1.6
%
See Note 5
Absolute Linearity
(1)
1
MI
(3)
V
w(n)(actual)
V
w(n)(expected)
Relative Linearity
(2)
0.2
MI
(3)
V
w(n + 1)
[V
w(n) + MI
]
Temperature Coefficient of R
TOTAL
300
ppm/C
See Note 5
Ratiometric Temperature
Coefficient
20
ppm/C
See Note 5
C
H
/C
L
/C
W
Potentiometer Capacitances
10/10/25
pF
See Circuit #3
I
AL
Rh, RI, Rw leakage current
0.1
10
A
Vin = Vss to Vcc. Device is in
stand-by mode.
X9421
REV 1.1.6 8/1/02
Characteristics subject to change without notice.
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D.C. OPERATING CHARACTERISTICS (Over the recommended operating conditions unless otherwise specified.)
ENDURANCE AND DATA RETENTION
CAPACITANCE
POWER-UP TIMING
POWER UP REQUIREMENTS (Power up sequencing can affect correct recall of the wiper registers)
The preferred power-on sequence is as follows: First V
CC
and then the potentiometer pins, R
H
, R
L
, and R
W
.
Voltage should not be applied to the potentiometer pins before V
CC
is applied. The V
CC
ramp rate specification
should be met, and any glitches or slope changes in the V
CC
line should be held to <100mV if possible. Also, V
CC
should not reverse polarity by more than 0.5V. Recall of wiper position will not be complete until V
CC
reaches its
final value.
Notes: (5) This parameter is periodically sampled and not 100% tested.
A.C. TEST CONDITIONS
Symbol
Parameter
Limits
Test Conditions
Min.
Typ.
Max.
Units
I
CC1
V
CC
Supply Current
(Active)
400
A
f
SCK
= 2MHz, SO = Open,
Other Inputs = V
SS
I
CC2
V
CC
Supply Current
(Non-volatile Write)
1
mA
f
SCK
= 2MHz, SO = Open,
Other Inputs = V
SS
I
SB
V
CC
Current (Standby)
1
A
SCK = SI = V
SS
, Addr. = V
SS
I
LI
Input Leakage Current
10
A
V
IN
= V
SS
to V
CC
I
LO
Output Leakage Current
10
A
V
OUT
= V
SS
to V
CC
V
IH
Input HIGH Voltage
V
CC
x 0.7
V
CC
+ 0.5
V
V
IL
Input LOW Voltage
0.5
V
CC
x 0.1
V
V
OL
Output LOW Voltage
0.4
V
I
OL
= 3mA
Parameter
Min.
Units
Minimum Endurance
100,000
Data Changes per Bit per Register
Data Retention
100
Years
Symbol
Test
Max.
Units
Test Conditions
C
OUT
(5)
Output Capacitance (SO)
8
pF
V
OUT
= 0V
C
IN
(5)
Input Capacitance (A0, SI, and SCK)
6
pF
V
IN
= 0V
Symbol
Parameter Max.
Max.
Units
t
R
V
CC
(5)
V
CC
Power up Ramp
0.2
50
V/msec
I
nput pulse levels
V
CC
x 0.1 to V
CC
x
0.9
Input rise and fall times
10ns
Input and output timing level
V
CC
x 0.5
X9421
REV 1.1.6 8/1/02
Characteristics subject to change without notice.
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AC TIMING
Symbol
Parameter
Min.
Max.
Units
f
SCK
SSI/SPI Clock Frequency
2.0
MHz
t
CYC
SSI/SPI Clock Cycle Time
500
ns
t
WH
SSI/SPI Clock High Time
200
ns
t
WL
SSI/SPI Clock Low Time
200
ns
t
LEAD
Lead Time
250
ns
t
LAG
Lag Time
250
ns
t
SU
SI, SCK, HOLD and CS Input Setup Time
50
ns
t
H
SI, SCK, HOLD and CS Input Hold Time
50
ns
t
RI
SI, SCK, HOLD and CS Input Rise Time
2
s
t
FI
SI, SCK, HOLD and CS Input Fall Time
2
s
t
DIS
SO Output Disable Time
0
500
ns
t
V
SO Output Valid Time
100
ns
t
HO
SO Output Hold Time
0
ns
t
RO
SO Output Rise Time
50
ns
t
FO
SO Output Fall Time
50
ns
t
HOLD
HOLD Time
400
ns
t
HSU
HOLD Setup Time
100
ns
t
HH
HOLD Hold Time
100
ns
t
HZ
HOLD Low to Output in High Z
100
ns
t
LZ
HOLD High to Output in Low Z
100
ns
T
I
Noise Suppression Time Constant at SI, SCK, HOLD and CS inputs
20
ns
t
CS
CS Deselect Time
2
s
t
WPASU
WP, A0 and A1 Setup Time
0
ns
t
WPAH
WP, A0 and A1 Hold Time
0
ns
EQUIVALENT A.C. LOAD CIRCUIT
Circuit #3 SPICE Macro Model
5V
1533
100pF
SDA Output
2.7V
100pF
10pF
R
H
R
TOTAL
C
H
25pF
C
W
C
L
10pF
R
W
R
L
X9421
REV 1.1.6 8/1/02
Characteristics subject to change without notice.
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HIGH-VOLTAGE WRITE CYCLE TIMING
XDCP TIMING
SYMBOL TABLE
Symbol
Parameter
Typ.
Max.
Units
t
WR
High-voltage Write Cycle Time (Store Instructions)
5
10
ms
Symbol
Parameter
Min.
Max. Units
t
WRPO
Wiper Response Time After The Third (Last) Power Supply Is Stable
10
s
t
WRL
Wiper Response Time After Instruction Issued (All Load Instructions)
10
s
t
WRID
Wiper Response Time From An Active SCL/SCK Edge (Increment/Decrement
Instruction)
450
ns
WAVEFORM
INPUTS
OUTPUTS
Must be
steady
Will be
steady
May change
from Low to
High
Will change
from Low to
High
May change
from High to
Low
Will change
from High to
Low
Don't Care:
Changes
Allowed
Changing:
State Not
Known
N/A
Center Line
is High
Impedance
X9421
REV 1.1.6 8/1/02
Characteristics subject to change without notice.
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TIMING DIAGRAMS
Input Timing
Output Timing
Hold Timing
...
CS
SCK
SI
SO
MSB
LSB
High Impedance
t
LEAD
t
H
t
SU
t
FI
t
CS
t
LAG
t
CYC
t
WL
...
t
RI
t
WH
...
CS
SCK
SO
SI
ADDR
MSB
LSB
t
DIS
t
HO
t
V
...
...
CS
SCK
SO
SI
HOLD
t
HSU
t
HH
t
LZ
t
HZ
t
HOLD
t
RO
t
FO
X9421
REV 1.1.6 8/1/02
Characteristics subject to change without notice.
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XDCP Timing (for All Load Instructions)
XDCP Timing (for Increment/Decrement Instruction)
Write Protect and Device Address Pins Timing
...
CS
SCK
SI
MSB
LSB
V
W
t
WRL
...
SO
High Impedance
...
CS
SCK
SO
SI
ADDR
t
WRID
High Impedance
V
W
...
Inc/Dec
Inc/Dec
...
CS
WP
A0
A1
t
WPASU
t
WPAH
(Any Instruction)
X9421
REV 1.1.6 8/1/02
Characteristics subject to change without notice.
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APPLICATIONS INFORMATION
Electronic potentiometers provide three powerful application advantages: (1) the variability and reliability of a solid-
state potentiometer, (2) the flexibility of computer-based digital controls, and (3) the retentivity of nonvolatile
memory used for the storage of multiple potentiometer settings or data.
Basic Configurations of Electronic Potentiometers
Basic Circuits
V
R
V
W
V
R
I
Three terminal Potentiometer;
Variable voltage divider
Two terminal Variable Resistor;
Variable current
V
H
V
L
Noninverting Amplifier
Voltage Regulator
Offset Voltage Adjustment
Comparator with Hysterisis
+
V
S
V
O
R
2
R
1
V
O
= (1+R
2
/R
1
)V
S
R
1
R
2
I
adj
V
O
(REG) = 1.25V (1+R
2
/R
1
)+I
adj
R
2
V
O
(REG)
V
IN
317
+
V
S
V
O
R
2
R
1
V
UL
= {R
1
/CR
1
+R
2
} V
O
(max)
V
LL
= {R
1
/CR
1
+R
2
} V
O
(min)
100K
10K
10K
10K
-12V
+12V
TL072
+
V
S
V
O
R
2
R
1
}
}
+5V
5V
LM308A
Cascading Techniques
Buffered Reference Voltage
+
+5V
R
1
+V
5V
V
W
V
W
V
OUT
= V
W
OP-07
V
W
V
W
+V
+V
+V
X
(a)
(b)
X9421
REV 1.1.6 8/1/02
Characteristics subject to change without notice.
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PACKAGING INFORMATION
16-Lead Plastic SOIC (300 Mil Body) Package Type S
NOTE: ALL DIMENSIONS IN INCHES (IN PARENTHESES IN MILLIMETERS)
0.014 (0.35)
0.020 (0.51)
PIN 1
PIN 1 INDEX
0.050 (1.27)
0.403 (10.2 )
0.413 ( 10.5)
(4X) 7
0.420"
0.050" Typical
0.030" Typical
16 Places
FOOTPRINT
0.010 (0.25)
0.020 (0.50)
0.0075 (0.19)
0.010 (0.25)
0
8
X 45
0.050"
Typical
0.290 (7.37)
0.299 (7.60)
0.393 (10.00)
0.420 (10.65)
0.003 (0.10)
0.012 (0.30)
0.092 (2.35)
0.105 (2.65)
0.015 (0.40)
0.050 (1.27)
X9421
REV 1.1.6 8/1/02
Characteristics subject to change without notice.
20 of 21
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PACKAGING INFORMATION
NOTE: ALL DIMENSIONS IN INCHES (IN PARENTHESES IN MILLIMETERS)
14-Lead Plastic, TSSOP, Package Type V
See Detail "A"
.031 (.80)
.041 (1.05)
.169 (4.3)
.177 (4.5)
.252 (6.4) BSC
.025 (.65) BSC
.193 (4.9)
.200 (5.1)
.002 (.05)
.006 (.15)
.047 (1.20)
.0075 (.19)
.0118 (.30)
0 - 8
.010 (.25)
.019 (.50)
.029 (.75)
Gage Plane
Seating Plane
Detail A (20X)
X9421
REV 1.1.6 8/1/02
Characteristics subject to change without notice.
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LIMITED WARRANTY
Devices sold by Xicor, Inc. are covered by the warranty and patent indemnification provisions appearing in its Terms of Sale only. Xicor, Inc. makes no warranty,
express, statutory, implied, or by description regarding the information set forth herein or regarding the freedom of the described devices from patent infringement.
Xicor, Inc. makes no warranty of merchantability or fitness for any purpose. Xicor, Inc. reserves the right to discontinue production and change specifications and prices
at any time and without notice.
Xicor, Inc. assumes no responsibility for the use of any circuitry other than circuitry embodied in a Xicor, Inc. product. No other circuits, patents, or licenses are implied.
TRADEMARK DISCLAIMER:
Xicor and the Xicor logo are registered trademarks of Xicor, Inc. AutoStore, Direct Write, Block Lock, SerialFlash, MPS, and XDCP are also trademarks of Xicor, Inc. All
others belong to their respective owners.
U.S. PATENTS
Xicor products are covered by one or more of the following U.S. Patents: 4,326,134; 4,393,481; 4,404,475; 4,450,402; 4,486,769; 4,488,060; 4,520,461; 4,533,846;
4,599,706; 4,617,652; 4,668,932; 4,752,912; 4,829,482; 4,874,967; 4,883,976; 4,980,859; 5,012,132; 5,003,197; 5,023,694; 5,084,667; 5,153,880; 5,153,691;
5,161,137; 5,219,774; 5,270,927; 5,324,676; 5,434,396; 5,544,103; 5,587,573; 5,835,409; 5,977,585. Foreign patents and additional patents pending.
LIFE RELATED POLICY
In situations where semiconductor component failure may endanger life, system designers using this product should design the system with appropriate error detection
and correction, redundancy and back-up features to prevent such an occurrence.
Xicor's products are not authorized for use in critical components in life support devices or systems.
1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to
perform, when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user.
2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life
support device or system, or to affect its safety or effectiveness.
Xicor, Inc. 2000 Patents Pending
ORDERING INFORMATION
Device
V
CC
Limits
Blank = 5V 10%
2.7 = 2.7 to 5.5V
Temperature Range
Blank = Commercial = 0C to +70C
I = Industrial = 40C to +85C
Package
S = 16-Lead SOIC
V = 14-Lead TSSOP
Potentiometer Organization
W =10K
Y =2.5K
X9421
P
T
V
Y
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